What effect do pressure treated fire retardants have on wood?

The use of pressure-treated fire retardants on wood is primarily aimed at enhancing the material's fire resistance. When fire retardants are applied to wood, they chemically alter the wood's properties in a way that slows down the combustion process. This means that the treated wood is less likely to ignite quickly and burns at a slower rate when exposed to flames. The retardants work by inhibiting the development of flames and reducing the amount of heat produced during combustion, thereby providing additional time for evacuation in case of a fire and helping to limit the spread of flames.

While factors like rigidity, weight, and insulation properties may be influenced by other treatments or processes, the central characteristic of pressure-treated fire retardants is their ability to modify the fire behavior of wood effectively. This makes option C the most accurate choice related to the function of fire retardants in treating wood.